Investigation of the interaction of sodium nitrite with hydrogen peroxide in aqueous solutions by the chemiluminescence method

An investigation is made of the chemiluminescence (luminol-dependent and spontaneous) of aqueous solutions of NaNO₂ and H₂O₂ in the pH range of 4.0–9.0. In the presence of luminol at pH>7 the initiator of luminescence is H₂O₂. At pH<7 the luminescence revealed seems to be initiated by peroxynitric acid (HOONO) produced by the interaction of NaNO₂ with H₂O₂ in weakly acid and acid solutions. Cysteine added to the solution prior to introducing H₂O₂ completely suppresses luminescence development in the pH range investigated. Moreover, cysteine quenches the luminescence already developed. Mannite and ethanol do not exert a substantial influence on the development of the luminescence. The solution of NaNO₂ and H₂O₂ is also characterized by spontaneous chemiluminescence, the intensity of which is one-two orders of magnitude lower than that of the luminol-dependent chemiluminescence. The intensity of the spontaneous chemiluminescence of the solutions of NaNO₂ and H₂O attains its maximum in the pH region of 6.5 to 7.0. It is assumed that the revealed spontaneous luminescence of the solutions of NaNO₂ and H₂O₂ is also attributable to formation of peroxynitrit acid in an activated state (HOONO^*). Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 3, pp. 436–440, May–June, 1999.